This application is generally related to earlier-filled, commonly-assigned patents and applications of Crooks et al, including U.S. Pat. Nos. 4,297,637; 4,318,043; 4,471,305; 4,599,565; 4,607,225; the pending application of Arakawa et al, Ser. No. 827,609, filed Feb. 10, 1985, now U.S. Pat. No. 4,695,801; pending application of Harrison et al., Ser. No. 827,638 filed Feb. 10, 1986, now U.S. Pat. No. 4,682,125; and the co-pending applications of Arakawa et al., Ser. No. 888,074 filed July 22, 1986, now U.S. Pat. No. 4,752,736 and of Fehn et al, Ser. No. 878,369, filed June 25, 1986 now U.S. Pat. No. 4,707,664. The contents of these related patents and applications are hereby incorporated by reference.
Magnetic resonance imaging (MRI) is now coming into widespread commercial usage. However, there are still many areas of MRI technology which need improving. One such area of improvement involves what is commonly referred to as an MRI "surface coil" convenient for accurate positioning arrangements (to examine, for example, anatomical areas of the head such as the temporomandibular joint and middle ear). MRI Surface coils of the variety used for imaging the temporomandibular joint offer distinct advantages over larger head or body coils for reasons well known in the art.
In imaging operations using an MRI RF surface coil, it is known that oblique surface coil imaging of the temporomandibular joint is an exacting procedure and requires very precise positioning and securing of the imaging device on the area being examined. It is also known that the surface coil should be oriented with its housing (sometimes referred to as a "pad") positioned directly next to the patient. Further, care should be taken to ensure that no gaps exist between the patient's face and the surface coil.
It is desirable that the MRI imaging device be positioned and tightly secured at an exact reproducible angle on the face, eye or other head part in order to obtain consistent and meaningful diagnostic data. Often, it is necessary to position the surface coil in a series of slightly different orientations in order to complete an effective examination. Thus, it is highly desirable to provide an ability to position and secure the coil in a precise and consistent manner. It may also be advantageous to position the surface coil in the same manner on different patients for purposes of comparative evaluation of different received images. It may also be necessary to repeat a particular surface imaging operation on the same patient (such as after treatment), thereby requiring that the surface coil be placed in substantially the same location and in the same orientation on the body part.
However, conventional holders for surface coils do not effectively permit such apparatus to be accurately positioned and secured in the different orientations required during an imaging operation. Typically, the surface coil is simply taped to the anatomical part to be examined. Further, the prior art methods and apparatus for imaging using an MRI RF surface coil have been incapable of orienting the surface coil such that it provides optimum signal-to-noise ratios. Prior art devices have also not been successful at duplicating an exact position of a previous imaging operation, nor have they been effective in duplicating positions on different patients.
The reader's attention is directed to the publications and patents discussed below as possibly relevant prior art:
______________________________________ Inventor U.S. Pat. No. Date Issued ______________________________________ Brown 4,608,977 September 2, 1986 Patil 4,592,352 June 3, 1986 Barbier et al 4,465,069 August 14, 1984 Patil et al 4,463,758 August 7, 1984 Perry 4,341,220 July 27, 1982 Kopf et al 4,256,112 March 17, 1981 Travis et al 3,025,397 March 13, 1962 ______________________________________
The '977 patent to Brown discloses a tomography-related system in which a frame is fixed to the body part being examined and operates in conjunction with a CT scanner and display apparatus. The frame includes a holder for guiding the desired therapeutic instrument and structure for providing reference indications of the location of the therapeutic equipment.
The '352 patent to Patil concerns a computer-assisted tomography stereotactic system in which a pair of vertically-disposed support members are longitudinally movable and mounted at opposite sides of a platform having selectively and vertically movable carrier supports.
The '069 patent to Barbier et al discloses an apparatus whereby the head of the patient is held in place horizontally using an indexed sliding cradle for an X-ray scanner. A vertical ring encircles the head and includes rest supports behind the ears and behind the eyes at the cheekbone area. An adjustable, horizontally-projecting instrument support structure is mounted on an arcuate track in the ring between the head rests.
The '758 patent to Patil et al discloses a tomography stereotatic frame for use with a CT scanner which comprises a platform for support having an area for supporting the patient's head. An inverted, substantially U-shaped frame is movably mounted on the support. A "probe holder" is movably mounted on either of the leg portions of the frame to permit a drill or probe to be extended therethrough.
The '220 patent to Perry also relates to a stereotatic surgery frame which is fixed to the patient's anatomy. The frame defines a predetermined, three-dimensional coordinate system in which surgical devices may be precisely positioned.
The '112 patent to Kopf et al concerns a head positioner for radiological and other medical procedures in which the components are secured to form a unitary head band structure capable of repeated and periodic use in positioning the cranium of a human skull in precisely the same position relative to other medical equipment.
The '397 patent to Travis et al discloses skull radiography apparatus comprising a skull receiving tray which is pivotally mounted on a base plate about an axis parallel to the longitudinal axis of the tray. An "aligner rod" overlying the tray provides swinging movement about the tray axis. The '397 structure also includes means on the base plate indicating the angular position of the rod.
It has now been found that the various deficiencies associated with prior art devices and the methods for positioning and securing surface coils on desired anatomical areas such as the temporomandibular joint may be substantially alleviated by the apparatus and method according to the present invention.
In particular, the apparatus according to the invention provides four separate means for positioning and securing the MRI RF surface coil relative to the temporomandibular joint or other anatomical part being imaged. The exemplary apparatus according to the invention also provides means for positioning and securing the anatomical part itself (as opposed to adjustment of the surface coil), thereby providing fifth and sixth means for independently positioning and securing the coil in an exact orientation relative to the body part being examined.
In essence, the present invention includes an adjustable holder for magnetic resonance imaging comprising means for positioning and securing the imaging device at a first predetermined point along the longitudinal axis of the holder, together with means for positioning and securing the imaging device at a second predetermined point transverse to the longitudinal axis of the holder and at a radial distance R from the longitudinal axis. In this regard, those skilled in the art will recognize that the longitudinal axis of the surface coil holder will be parallel to, but not necessarily the same as, the true longitudinal axis (e.g. the "Z-axis") of the remainder of an MRI imaging system within which the surface coil operates.
The four independently adjustable positioning and securing means for the surface coil holder in accordance with the invention provide an operator with considerable flexibility in locating the coil at the exact desired position and orientation relative to the body part being examined.
First, means are provided whereby the surface coil holder may be positioned and secured at any point along the longitudinal axis of the holder using a pair of opposing "runner feet" which are slidably mounted to the holder base plate, thereby enabling the holder to move back and forth in a longitudinal direction. Second, a pair of parallel, generally U-shaped orientation guides transverse to the longitudinal axis (referred to herein as coil orientation "runner guides") allow for orbital movement of the surface coil to any desired radial point at a distance R from the longitudinal axis. Third, the surface coil can be adjusted by pivotal rotation of the coil about an axis which is substantially parallel to the longitudinal axis. Fourth, the coil can be moved radially inwardly and outwardly relative to the patient's head by way of an adjustable orientation arm operatively connected to clamping and adjusting means on the U-shaped runner guides.
The objective of using the above four independently adjustable positioning and securing means is to enable the operator to place the coil in an exact orientation flat against the body part to be examined during imaging.
In contrast to the above four means for positioning the MRI RF surface coil itself, the present invention also contemplates two separate means for positioning the body part to be examined. In particular, the support structure for the body part (such as the temporomandibular joint area of the head) may be rotated (and then secured) about an axis parallel to the longitudinal axis of the holder at an oblique angle of up to 45 degrees. A sixth means for positioning anatomical parts is accomplished by way of longitudinal, as opposed to rotational, adjustment of the support structure for the body part.
Thus, it is an object of the present invention to provide for an improved apparatus for imaging anatomical body parts such as the temporomandibular joint or middle ear using an RF MRI surface coil.
It is a further object of the present invention to provide and an improved holder for an MRI RF surface coil having means for adjustably positioning and securing the surface coil to an exact position and angle relative to the anatomical area to be imaged.
It is still a further object of the present invention to provide means for obliquely imaging the temporomandibular joint in a very exacting manner which can be documented and duplicated upon subsequent imaging operation.
These and other objects of the invention will become more clear following a review of the appended drawings, and detailed specification.